West Bengal, Bihar to remain red zone for aerosol pollution in 2023, predicts study

A recent study by scientists from Bose Institute in Kolkata has revealed that aerosol pollution in West Bengal is anticipated to rise by 8% and continue to remain in the “highly vulnerable” red zone for aerosol pollution. This is the second highest forecasted aerosol pollution level in the country after Bihar.

Details of the study were published in a paper titled ‘ A deep insight into state-level aerosol pollution in India: Long-term (2005–2019) characteristics, source apportionment, and future projection (2023)’ in a journal by Elsevier group.

The study by Abhijit Chatterjee, Associate Professor of Environmental Sciences at Bose Institute, and Ph.D. scholar Monami Dutta, provides a national scenario of aerosol pollution with the long-term (2005–2019) trend, source apportionment, and future scenario (2023) for various Indian states.

High aerosol amounts include particulate matter (PM2.5 and PM10) among other pollutants as well as sea salt, dust, black and organic carbon. If inhaled they can be harmful to people’s health. Aerosol optical depth (AOD) is the quantitative estimate of the aerosol present in the atmosphere and it can be used as a proxy measurement of PM _2.5.

“The mean AOD over the long-term period of 2005–2019 shows high values (>0.65) over IGP (Indo Gangetic Plain)… West Bengal and Bihar are the two States at IGP showing the highest rate of AOD increase (~0.015 yr−1) Rajasthan at the westernmost, Jammu and Kashmir at the northernmost, and most of the north-eastern parts of India exhibited the slowest rate of AOD increase,” the paper states.

The values of AOD range from 0 and 1.0 indicating a crystal-clear sky with maximum visibility whereas a value of 1 indicates very hazy conditions. AOD values less than 0.3 falls under the green zone (safe), 0.3-0.4 is the blue zone (less vulnerable), 0.4-0.5 is orange (vulnerable) while over 0.5 is the red zone (highly vulnerable).

“Due to its strategic location, West Bengal receives Indo Gangetic Plain air pollution outflows and its local emissions have put West Bengal in the highly vulnerable zone. West Bengal is already in the highly vulnerable zone; a nominal increase (approximately 8% projected increase in AOD) can cause a disastrous impact on the health and life of the people residing in this state,” Abhijit Chatterjee, principal author of this study said.

Monami Dutta, first-author of the study and Senior Research Fellow, at Bose Institute, Kolkata said that  among major aerosol pollution sources for West Bengal, from 2005 to 2014, vehicular emissions (40-42%) remained the top source of pollution mostly in big cities of the state followed by vehicular driven dust (18-20%) and solid fuel burning (13-15%).

Ms. Dutta said that from 2015 onwards to 2019, solid fuel burning (35%) became the major emission source while the contribution of vehicular emissions (18%) dropped becoming the least.  “The reason for the drop in vehicular emissions could be due to the introduction of EURO-IV fuel standards and up-gradation of engines, ban on 15-year-old vehicles, etc. At the same time, vehicular-driven dust was replaced by construction-driven dust which is a result of over urbanization,” she added.

The researcher said that the dominance of solid fuel burning in recent years could be because of the unregistered and overabundant numerous roadside eateries, restaurants, etc. across major cities in West Bengal.

The study points out that the future projection clearly shows that central, coastal, and southern India would become highly vulnerable in 2023 if the respective sources continue to dominate.  “Reduction in the thermal power plant emissions alone could effectively reduce aerosol pollution and move vulnerable states into safe and less vulnerable (states),” the paper said.